Generally, an electronic apparatus is provided with a narrow slot or an insertion slot, into which an access device can be inserted. The access device inserted into the slot can be programmed, or can read data stored in the electronic apparatus or write data into the electronic apparatus. The slot is internally provided with a plurality of terminals, which electrically contact with terminals correspondingly provided in the access device to achieve the purpose of power supplying, data transmission or online operation on the electronic apparatus. While the rapidly developed electronic technology brings a lot of conveniences to users, the users also encounter with many security problems in using various electronic apparatuses. For example, users' information and data stored in the electronic apparatuses are subject to the risk of being stolen or illegally copied by other unauthorized users. Therefore, it is necessary to provide safety devices for the slots on electronic apparatuses to limit the access of the slot by unauthorized users.